Essential in the control of rheumatic fever and in the prevention of rheumatic heart disease is the proper management of streptococcal upper respiratory tract infection. Before this can be finally accomplished, information about individual susceptibility to streptococcal infections as well as information about the epidemiology of the spread of streptococci among contacts of infected individuals and carriers must be made available. The primary objective of this study is to investigate new and improved methods of diagnosis and control of streptococcal upper respiratory tract infections--while at the same time learning more about the epidemiology of the spread of group A beta hemolytic streptococci. This information may ultimately lead to a reduction in the incidence of rheumatic fever and theraby reduce the morbidity from rheumatic heart disease, a condition which remains high as a cause of significant cardiovascular disease. The second year of this study will be carried out among index cases of pharyngitis and their family contacts seen in a clinic-emergency room setting. Clinical observations and both established and new laboratory techniques will be serially obtained and correlated to assist in identifying and documenting host and bacterial risk factors affecting the epidemiology of streptococcal infections and in differentiating bona fide streptococcal infections from the carrier state. BIBLIOGRAPHIC REFERENCES: Kaplan, E.L. and Wannamaker, L.W.: The C-reactive protein in streptococcal pharyngitis. Pediatrics, in press (July 1977). Kaplan, E.L. and Wannamaker, L.W.: The C-reative protein (CRP) in streptococcal pharyngitis. Abstracts of the Midwest Society for Pediatric Research, 1976.